Overbased metal-containing detergents

ABSTRACT

Phenate overbased detergents with high TBN: % surfactant ratios are useful lubricant additives

This invention relates to compositions suitable, inter alia, aslubricant additives, and especially to calcium overbased detergents, andmore especially to such materials suitable for use as additives tolubricants for use in marine engines.

To meet intense pressures on capital, maintenance, and running costs,marine engine manufacturers are producing new engines designed tominimize fuel and lubricant consumption, and are placing heavy demandson suppliers to provide lubricants that reduce wear and extend theperiod between overhauls. There is a continuing need for lubricantadditives that provide detergency, antioxidant properties, and rustprotection, and that neutralize corrosive acids from sulphur-containingfuels. Overbased detergents are uniquely able to fulfil all of thesenecessary roles.

Lubricant formulators are, as a result of the requirements placed onthem by engine manufacturers and users, in turn seeking higher totalbase number (TBN) overbased detergents, in order to reduce the treatrate while maintaining so effectiveness. (In this specification, the TBNof an overbased detergent is the TBN, in mg KOH/g, as measured by ASTMD2896.) There is also a need for products which, while being highlyeffective as additives, can be more cost-effective than existingproducts, and which are relatively easy to prepare and to handle.

Overbased metal-containing detergents suitable for use as lubricantadditives are typically prepared as concentrates in oil. In suchconcentrates, a basic metal-containing material is maintained indispersion or solution in the oil by a surfactant system comprising, forexample, phenate, salicylate, sulphonate or naphthenate anions.

Overbased detergents initially contained a single type of anion, forexample a member or members of the phenate group, or of the sulphonategroup, but for many years compositions have been available that containanions of two or more such groups, obtained either by adding two or moreoverbased detergents having different types of anion or by themanufacture of a hybrid material in which two or more anions ofdifferent groups are incorporated during the overbasing process. Asbasic materials, compounds of members of the alkali and alkaline earthgroups are used, compounds of calcium being most frequently employed.

For a number of applications, for example, for lubricants for use inmarine engines, it may in some cases be desirable, for maximumeffectiveness, that overbased detergents contain a relatively highproportion of phenate and salicylate anions. Such overbased detergentsmay also be useful in other applications.

The present invention provides a calcium overbased detergent comprisinga surfactant system derivable, and preferably derived, from at least twosurfactants, at least one of which is a sulphurized or non-sulphurizedphenol or a derivative thereof and the other, or at least one other, ofwhich is a surfactant other than a phenol surfactant, the proportion,measured as described herein, of the said phenol in the surfactantsystem being at least 15 mass %, and the overbased detergent having aTBN: % surfactant ratio (as hereinafter defined) of at least 21.

By a “calcium overbased detergent” is meant an overbased detergent inwhich the metal cations of the basic metal-containing material areessentially calcium cations. Small amounts of other cations may bepresent in the basic metal-containing material, but typically at least80 mole %, more typically at least 90 mole %, for example at least 95mole %, of the cations in the basic metal-containing material, arecalcium ions. Cations other than calcium may be derived, for example,from the use in the manufacture of the overbased detergent of asurfactant salt in which the cation is a metal other than calcium.

The percentage of surfactant in the overbased detergent, and thepercentages of the individual surfactants, for example, phenol, in thesurfactant system, are the percentages measured by the method set outbelow, which also indicates how the “standardized TBN” of an overbaseddetergent is determined.

1. Dialysis of the Overbased Detergent and Determination of StandardizedTBN

A known amount (A g, approximately 20 g) of the liquid overbaseddetergent (substantially free from other lubricating oil additives) isdialysed through a membrane in a Soxhlet extractor (150 mm height×75 mminternal diameter) using n-hexane siphoning at a rate of 3 to 4 timesper hour for 20 hours. The membrane should be one which retainssubstantially all the metal-containing material and passes substantiallyall the remainder of the sample. An example of a suitable membrane is agum rubber membrane supplied by Carters Products, Division of CarterWallace inc., New York, N.Y. 10105 under the trade name Trojans. Thedialysate and residue obtained on completion of the dialysis step areevaporated to dryness, any remaining volatile material then beingremoved in a vacuum oven (100° C. at less than 1 torr or less than about130 Pa). The mass of the dried residue, in grams, is designated B. Thepercentage (C) of overbased detergent material in the liquid sample isgiven by the equation: $C = {\frac{B}{A} \times 100\quad \%}$

The “standardized TBN” of the overbased detergent (that is, the TBNexpressed in a manner which is independent of the amount of diluent) isthe TBN measured according to ASTM D2896 on the dried residue.

Background information for the dialysis technique is given by Amos, R.and Albaugh, E. W. in “Chromatography in Petroleum Analysis”, Altgelt,K. H. and Gouw, T. H., Eds, pages 417 to 422, Marcel Dekker, Inc., NewYork and Basel, 1979.

2. Determination of TBN % Total Surfactant Ratio

A known amount (D g, approximately 10 g) of the dried residue ishydrolyzed as specified in sections 8.1 to 8.1.2 of ASTM D3712, exceptthat at least 200 ml of 25% by volume hydrochloric acid (sp. gr. 1.18)is used in section 8.1.1. The amount of hydrochloric acid used should besufficient to effect acidification/hydrolysis of the overbased detergentresidue into organic materials (surfactants) and inorganic materials(calcium-containing materials, for example, calcium chloride). Thecombined ether extracts are dried by passing them through anhydroussodium sulphate. The sodium sulphate is rinsed with clean ether, and thecombined ether solutions are evaporated to dryness (at approximately110° C.) to yield a hydrolyzed residue. The mass of the dried hydrolyzedresidue, in grams, is designated E.

The percentage, Y, of total surfactants in the original liquid overbaseddetergent is given by the equation $Y = {\frac{E}{D} \times C}$

and the TBN: % total surfactant ratio, X, is given by the equation$X = \frac{{TBN}\quad {of}\quad {the}\quad {liquid}\quad {overbased}\quad {detergent}}{Y}$

It will be noted that, in determining X, the mass of the surfactants intheir free form (that is, not in the form of a salt or other derivative)is used. For brevity, X will in general be referred to herein as the“TBN % surfactant ratio”, and it is the value of X that is specifiedunder this term in the claims and elsewhere in this specification.

3. Determination of Individual Surfactants (In Their Free Form) in theSurfactant System

The techniques described below isolate the individual surfactants, inhydrolyzed form, from the hydrolyzed surfactant mixture derived from theoverbased detergent. As indicated below, the proportion of eachindividual surfactant is the proportion by mass of the individualsurfactant, in hydrolyzed form, in the hydrolyzed surfactant mixture.Thus, where, for example, the overbased detergent contains a calciumphenate/sulphonate/salicylate surfactant system, the proportions of theindividual surfactants in the surfactant system are expressed as theproportions of phenol, sulphonic add and salicylic acid respectively.

The proportions of individual surfactants may be determined by thefollowing method.

A known amount (F g, approximately 1 g) of the dried hydrolyzed residueobtained as described above is placed at the top of a 450×25 mm(internal diameter) fritted glass column filled with 60-100 US meshFlorisil. Florisil is magnesium silicate with a CAS number of 8014-97-9.The column is eluted with a 250 ml portion of each of seven solvents ofincreasing polarity, namely, heptane, cyclohexane, toluene, ethyl ether,acetone, methanol, and, lastly, a mixture of 50 volume % chloroform, 44volume % isopropanol, and 6 volume % ammonia solution (sp. gr. 0.88).Each fraction is collected, evaporated to dryness, and the resultingresidue is weighed and then analyzed to determine the amount (G¹, G², G³. . . g) and nature of the surfactant(s) contained in the fraction.

Analysis of the fractions (or of the hydrolyzed residue) can be carriedout by, for example, chromatographic, spectroscopic, and/or titration(colour indicator or potentiometric) techniques known to those skilledin the art. Where the overbased detergent contains a sulphonatesurfactant and a salicylate surfactant, the sulphonic acid and salicylicacid obtained by hydrolysis of these surfactants will usually be elutedfrom the column together. In this case, and in any other case where itis necessary to determine the proportion of sulphonic acid in a mixturecontaining it, the proportion of sulphonic acid in the mixture can bedetermined by the method described by Epton in Trans. Far. Soc. April1948, 226.

In the above method, the mass (in grams, designated H¹) of a givensurfactant, in hydrolyzed form, is determined from the fraction(s)containing it, and thus the proportion of that surfactant in thesurfactant system of the original overbased detergent is$\frac{H^{1}}{F} \times 100\quad \%$

The percentages (by mass) of the individual surfactants (in their freeform, that is, not in the form of a salt or other derivative) based onthe surfactant system can be predicted from the proportions of thesurfactants used as starting materials, provided that the percentage of“reactive ingredient” is known for each of the surfactant startingmaterials. (The term “reactive ingredient” is defined in Note 1 toTables 1 and 2 in the Examples in this specification.) The percentage ofthe total surfactants (in their free form) in the liquid overbasedproduct can then be predicted, and the TBN: % surfactant ratio can bedetermined. Further, the standardized TBN can be predicted, providedthat the proportion of the overbased detergent material in the liquidoverbased product (that is, the proportion of the liquid overbasedproduct that is not oil or non-reactive surfactant material) is known.

Good correlation has been found between predicted values and valuesmeasured as described above.

The overbased detergents according to the invention are preferablyhybrid overbased detergents, that is, overbased detergents obtained byoverbasing a mixture containing two or more surfactants. At least one ofthe surfactants in a mixture to be overbased may be present in apreviously prepared overbased detergent.

The present invention also provides a method of manufacturing a calciumoverbased detergent having a surfactant system derived from at least twosurfactants, which method comprises treating with an overbasing agent(as hereinafter defined) a mixture comprising:

(a) at least two surfactants, at least one of which is a sulphurized ornon-sulphurized phenol or a derivative thereof, and the other, oranother, of which is a surfactant other than a phenol surfactant;

(b) at least one basic calcium compound; and

(c) oil, treatment with the overbasing agent being carried out in atleast one step, preferably at least two steps, at less than 100° C., thetotal proportion, measured as described herein, of the said phenol inthe surfactant system of the overbased detergent being at least 15 mass%, and the overbased detergent having a TBN: % surfactant ratio of atleast 21.

It will be appreciated that the mixture to be overbased contains freebasic calcium compound(s), that is, basic calcium compound(s) whichis/are available to react with the overbasing agent. By an “overbasingagent” is meant an agent or compound capable of reacting with the basiccalcium compound(s) (b) to form a basic calcium-containing materialwhich can be maintained in dispersion or solution in the oil by thesurfactant system. Where there is more than one overbasing step,different overbasing agents may, if desired, be used for the differentsteps. In any individual overbasing step, a mixture of differentoverbasing agents may, if desired, be used.

Examples of suitable overbasing agents are carbon dioxide, a source ofboron, for example, boric acid, sulphur dioxide, hydrogen sulphide, andammonia. Preferred overbasing agents are carbon dioxide or boric acid,or a mixture of the two. The most preferred overbasing agent is carbondioxide and, for convenience, the treatment with overbasing agent willin general be referred to as “carbonation”. Unless the context clearlyrequires otherwise, it will be understood that references herein tocarbonation include references to treatment with other overbasingagents.

Advantageously, on completion of the carbonation step(s), part of thebasic calcium compound(s) (b) remains uncarbonated. Advantageously, upto 15 mass % of the basic calcium compound(s) remains uncarbonated,especially up to 11 mass %.

As indicated above, carbonation is effected at less than 100° C.Typically carbonation is effected at at least 15° C., preferably atleast 25° C. Advantageously, carbonation is carried out at less than 80°C., more advantageously less than 60° C., preferably at most 50° C.,more preferably at most 40° C., and especially at most 35° C.Advantageously, the temperature is maintained substantially constantduring the or each carbonation step, with only minor fluctuations. Wherethere is more than one carbonation step, both or all carbonation stepsare preferably carried out at substantially the same temperature,although different temperatures may be used, if desired, provided thateach step is carried out at less than 100° C.

Carbonation may be effected at atmospheric, super-atmospheric orsub-atmospheric pressures. Preferably, carbonation is carried out atatmospheric pressure.

Advantageously, the first carbonation step (and preferably also thesecond or each subsequent carbonation step, if used) is followed by a“heat-soaking” step in which the mixture is maintained, without additionof any further chemical reagents, in a selected temperature range (or ata selected temperature), which is normally higher than the temperatureat which carbonation is effected, for a period before any furtherprocessing steps are carried out The mixture is normally stirred duringheat-soaking. Typically, heat-soaking may be carried out for a period ofat least 30 minutes, advantageously at least 45 minutes, preferably atleast 60 minutes, especially at least 90 minutes. Temperatures at whichheat-soaking may be carried out are typically in the range of from 15°C. to just below the reflux temperature of the reaction mixture,preferably 25° C. to 60° C.: the temperature should be such thatsubstantially no materials (for example, solvents) are removed from thesystem during the heat-soaking step. We have found that heat-soaking hasthe effect of assisting product stabilization, dissolution of solids,and filtrability.

Preferably, following the first carbonation step (and the heat-soakingstep, if used), a further quantity of basic calcium compound (component(b)) is added to the mixture and the mixture is again carbonated, thesecond carbonation step advantageously being followed by a heat-soakingstep.

Products of reduced viscosity may be obtained by employing one or morefurther additions of basic calcium compound and subsequent carbonation,each carbonation step advantageously being followed by a heat-soakingstep. This is one important aspect of the present invention. Further, wehave found that products of higher TBN, and higher TBN: % surfactantratio, with convenient viscosities, may be obtained by the use of thesteps mentioned in this paragraph. In each case, comparison is made withthe product resulting from treatment in fewer steps with the samequantity of the basic calcium compound and of the overbasing agent.

Basic calcium compounds for use in manufacture of the overbaseddetergents include calcium oxide, hydroxide, alkoxides, andcarboxylates. Calcium oxide and, more especially, hydroxide arepreferably used. A mixture of basic compounds may be used, if desired.

The mixture to be overbased by the overbasing agents should normallycontain water, and may also contain one or more solvents, promoters orother substances commonly used in overbasing processes.

Examples of suitable solvents are aromatic solvents, for example,benzene, alkyl-substituted benzenes, for example, toluene or xylene,halogen-substituted benzenes, and lower alcohols (with up to 8 carbonatoms), preferably aliphatic lower alcohols. Preferred solvents aretoluene and/or methanol. The amount of toluene used is advantageouslysuch that the percentage by mass of toluene, based on the calciumoverbased detergent (excluding oil) is at least 1.5, preferably at least15, more preferably at least 45, especially at least 60, more especiallyat least 90. For practical/economic reasons, the said percentage oftoluene is typically at most 1200, advantageously at most 600,preferably at most 500, especially at most 150. The amount of methanolused is advantageously such that the percentage by mass of methanol,based on the calcium overbased detergent (excluding oil) is at least1.5, preferably at least 15, more preferably at least 30, especially atleast 45, more especially at least 50. For practical/economic reasons,the said percentage of methanol (as solvent) is typically at most 800,advantageously at most 400, preferably at most 200, especially at most100.

The above percentages apply whether the toluene and methanol are usedtogether or separately.

Preferred promoters for use in accordance with the invention aremethanol and water. The amount of methanol used is advantageously suchthat the percentage by mass of methanol, based on the initial charge ofbasic calcium compound(s), for example, calcium hydroxide, (that is,excluding any basic calcium compound(s) added in a second or subsequentstep) is at least 6, preferably at least 60, more preferably at least120, especially at least 180, more especially at least 210. Forpractical/economic reasons, the said percentage of methanol (aspromoter) is typically at most 3200, advantageously at most 1600,preferably at most 800, especially at most 400. The amount of water inthe initial reaction mixture (prior to treatment with the overbasingagent) is advantageously such that the percentage by mass of water,based on the initial charge of basic calcium compound(s), for example,calcium hydroxide, (that is, excluding any basic calcium compound(s)added in a second or subsequent step) is at least 0.1, preferably atleast 1, more preferably at least 3, especially at least 6, moreespecially at least 12, particularly at least 20. For practical/economicreasons, the said percentage of water is typically at most 320,advantageously at most 160, preferably at most 80, especially at most40. If reactants used are not anhydrous, the proportion of water in thereaction mixture should take account of any water in the components andalso water formed by neutralization of the surfactants. In particular,allowance must be made for any water present in the surfactantsthemselves.

Advantageously, the reaction medium comprises methanol, water (at leastpart of which may be generated during salt formation), and toluene.

If desired, low molecular weight carboxylic acids (with 1 to about 7carbon atoms), for example, formic acid, inorganic halides, or ammoniumcompounds may be used to facilitate carbonation, to improvefiltrability, or as viscosity agents for overbased detergents. Theoverbased detergents in accordance with the invention can, however, beprepared by a process which does not require the use of an inorganichalide or ammonium salt catalyst, for example, ammonium salts of lowercarboxylic acids or of alcohols, and are preferably free from groupsderived from such a halide or ammonium catalyst. (Where an inorganichalide or ammonium salt is used in an overbasing process the catalystwill normally be present in the final overbased detergent.) Further, theoverbased detergents in accordance with the invention can be prepared bya process which does not require the use of reagents such as dihydricalcohols (for example, ethylene glycol) which are used when operating athigher temperatures; the overbased detergents of the invention arepreferably free from such dihydric alcohols or residues thereof.

The invention also provides overbased detergents prepared by the methodof the invention, concentrates comprising overbased detergents accordingto, or prepared according to, the invention, and oil-based compositions,particularly lubricating oils, especially lubricating oils for marineuse, comprising an overbased detergent according to, or preparedaccording to, the invention.

For ease of handling, an overbased detergent according to, or preparedin accordance with, the invention, advantageously has a KV₄₀ of at most20,000 mm²/s, preferably at most 10,000 mm²/s, especially at most 5,000mm²/s, and a KV₁₀₀ of at most 2,000 mm²/s, preferably at most 1,000mm²/s, especially at most 500 mm²/s. Throughout this specification,viscosities are measured in accordance with ASTM D445.

Overbased detergents according to the invention advantageously have aTBN of at least 300, more advantageously at least 330, preferably atleast 350, more preferably at least 400, especially at least 450. Asindicated later in this specification, an important aspect of thepresent invention is the provision of high TBN overbased detergents ofacceptable viscosity and containing a relatively high proportion ofphenate and salicylate surfactants in the surfactant system.

The invention also makes possible the provision of overbased detergentswith high standardized TBNs (as defined herein). Thus, for example, theoverbased detergents may have a standardized TBN of 450 or more,especially 460 or more, advantageously at least 500, more advantageouslyat least 550, preferably at least 600, more preferably at least 650.

The TBN: % surfactant ratio is an indication of the amount of(relatively expensive) surfactant required to prepare an overbaseddetergent of a specified TBN. The overbased detergents in accordancewith the invention have a TBN: % surfactant ratio of at least 21. Withappropriate starting materials/reaction conditions, ratios of up to 25or more, such as 30 or more, for example 35 or more, or 40 or more, maybe obtained. Independently of the TBN: % surfactant ratio, the totalproportion of the phenol in the surfactant system is advantageously atleast 25 mass %, more advantageously at least 35 mass %, preferably atleast 45 mass %, more preferably at least 55 mass %, especially at least70 mass %.

Surfactants from which the surfactant system of the overbased detergentsin accordance with, or prepared according to, the invention arederivable or derived preferably contain at least one hydrocarbyl group,for example, as a substituent on an aromatic ring. The term“hydrocarbyl” as used herein means that the group concerned is primarilycomposed of hydrogen and carbon atoms but does not exclude the presenceof other atoms or groups in a proportion insufficient to detract fromthe substantially hydrocarbon characteristics of the group.Advantageously, hydrocarbyl groups in surfactants for use in accordancewith the invention are aliphatic groups, preferably alkyl or alkylenegroups, especially alkyl groups, which may be linear or branched. Thetotal number of carbon atoms in the surfactants should be sufficient toimpart the desired oil-solubility.

When preparing overbased detergents in accordance with the invention oneor more of the surfactants may, if desired, be used in the form of aderivative thereof, provided that the derivative, if other than a metalsalt, can react with the basic calcium compound(s) (b) to form a calciumsalt of the surfactant. Unless this is clearly inappropriate in thecontext, references in the following discussion of individualsurfactants, and elsewhere in this specification, to surfactants intheir “free” (non-salted) form include references to appropriatederivatives of those surfactants. Examples of suitable derivatives ofcertain of the preferred surfactants are: ammonium salts, metal salts oresters of phenols; ammonium salts, metal salts, esters, anhydrides, acidchlorides or amides of salicylic acids; ammonium salts, metal salts,esters, anhydrides, acid chlorides or amides of carboxylic acids; andammonium salts, metal salts, esters or anhydrides of sulphonic acids.

Phenols used in accordance with the invention may be non-sulphurized or,preferably, sulphurized. Further, the term “phenol” as used hereinincludes phenols containing more than one hydroxyl group (for example,alkyl catechols) or fused aromatic rings (for example, alkyl naphthols)and phenols which have been modified by chemical reaction, for example,alkylene-bridged phenols and Mannich base-condensed phenols; andsaligenin-type phenols (produced by the reaction of a phenol and analdehyde under basic conditions).

Preferred phenols from which overbased detergents in accordance with theinvention may be derived are of the formula

where R represents a hydrocarbyl group and y represents 1 to 4. Where yis greater than 1, the hydrocarbyl groups may be the same or different.

In lubricating oil overbased detergents the phenols are frequently usedin sulphurized form. Sulphurized hydrocarbyl phenols may typically berepresented by the formula:

where x is generally from 1 to 4. In some cases, more than two phenolmolecules may be linked by S_(x) bridges.

In the above formulae, hydrocarbyl groups represented by R areadvantageously alkyl groups, which advantageously contain 5 to 100carbon atoms, preferably 5 to 40 carbon atoms, especially 9 to 12 carbonatoms, the average number of carbon atoms in all of the R groups beingat least about 9 in order to ensure adequate solubility in oil.Preferred alkyl groups are nonyl (tripropylene) groups.

In the following discussion, hydrocarbyl-substituted phenols will forconvenience be referred to as alkyl phenols.

A sulphurizing agent for use in preparing a sulphurized phenol orphenate may be any compound or element which introduces —(S)_(x)—bridging groups between the alkyl phenol monomer groups, wherein x isgenerally from 1 to about 4. Thus, the reaction may be conducted withelemental sulphur or a halide thereof, for example, sulphur dichlorideor, more preferably, sulphur monochloride. If elemental sulphur is used,the sulphurization reaction may be effected by heating the alkyl phenolcompound at from 50 to 250° C., and preferably at least 100° C. The useof elemental sulphur will typically yield a mixture of bridging groups—(S)_(x)— as described above. If a sulphur halide is used, thesulphurization reaction may be effected by treating the alkyl phenol atfrom −10° C. to 120° C., preferably at least 60° C. The reaction may beconducted in the presence of a suitable diluent. The diluentadvantageously comprises a substantially inert organic diluent, forexample mineral oil or an alkane. In any event, the reaction isconducted for a period of time sufficient to effect substantialreaction. It is generally preferred to employ from 0.1 to 5 moles of thealkyl phenol material per equivalent of sulphurizing agent.

Where elemental sulphur is used as the sulphurizing agent, it may bedesirable to use a basic catalyst, for example, sodium hydroxide or anorganic amine, preferably a heterocydic amine (e.g., morpholine).

Details of sulphurization processes are well known to those skilled inthe art.

Regardless of the manner in which they are prepared, sulphurized alkylphenols useful in preparing overbased detergents generally comprisediluent and unreacted alkyl phenols and generally contain from 2 to 20mass %, preferably 4 to 14 mass %, and most preferably 6 to 12 mass %,sulphur based on the mass of the sulphurized alkyl phenol.

As indicated above, the term “phenol” as used herein includes phenolswhich have been modified by chemical reaction with, for example, analdehyde, and Mannich base-condensed phenols.

Aldehydes with which phenols used in accordance with the invention maybe modified include, for example, formaldehyde, propionaldehyde andbutyraldehyde. The preferred aldehyde is formaldehyde. Aldehyde-modifiedphenols suitable for use in accordance with the present invention aredescribed in, for example, U.S. Pat. No. 5,259,967.

Mannich base-condensed phenols are prepared by the reaction of a phenol,an aldehyde and an amine. Examples of suitable Mannich base-condensedphenols are described in GB-A-2 121 432.

In general, the phenols may include substituents other than thosementioned above provided that such substituents do not detractsignificantly from the surfactant properties of the phenols. Examples ofsuch substituents are methoxy groups and halogen atoms.

In one preferred aspect of the invention, at least one of thesurfactants from which the surfactant system is derivable is a salicylicacid or a derivative thereof.

Salicylic acids used in accordance with the invention may benon-sulphurized or sulphurized, and may be chemically modified and/orcontain additional substituents, for example, as discussed above forphenols. Processes similar to those described above may also be used forsulphurizing a hydrocarbyl-substituted salicylic acid, and are wellknown to those skilled in the art. Salicylic acids are typicallyprepared by the carboxylation, by the Kolbe-Schmitt process, ofphenoxides, and in that case, will generally be obtained (normally in adiluent) in admixture with uncarboxylated phenol.

Preferred substituents in oil-soluble salicylic acids from whichoverbased detergents in accordance with the invention may be derived arethe substituents represented by R in the above discussion of phenols. Inalkyl-substituted salicylic acids, the alkyl groups advantageouslycontain 5 to 100 carbon atoms, preferably 9 to 30 carbon atoms,especially 14 to 20 carbon atoms.

In another aspect of the present invention, at least one of thesurfactants from which the surfactant system is derivable is a sulphonicacid or a derivative thereof.

Sulphonic acids used in accordance with this aspect of the invention aretypically obtained by sulphonation of hydrocarbyl-substituted,especially alkyl-substituted, aromatic hydrocarbons, for example, thoseobtained from the fractionation of petroleum by distillation and/orextraction, or by the alkylation of aromatic hydrocarbons. Examplesinclude those obtained by alkylating benzene, toluene, xylene,naphthalene, biphenyl or their halogen derivatives, for example,chlorobenzene, chlorotoluene or chloronaphthalene. Alkylation ofaromatic hydrocarbons may be carried out in the presence of a catalystwith alkylating agents having from about 3 to more than 100 carbonatoms, such as, for example, haloparaffins, olefins that may be obtainedby dehydrogenation of paraffins, and polyolefins, for example, polymersof ethylene, propylene, and/or butene. The alkylaryl sulphonic acidsusually contain from about 7 to about 100 or more carbon atoms. Theypreferably contain from about 16 to about 80 carbon atoms, or 12 to 40carbon atoms, per alkyl-substituted aromatic moiety, depending on thesource from which they are obtained.

When neutralizing these alkylaryl sulphonic acids to providesulphonates, hydrocarbon solvents and/or diluent oils may also beincluded in the reaction mixture, as well as promoters and viscositycontrol agents.

Another type of sulphonic acid which may be used in accordance with theinvention comprises alkyl phenol sulphonic acids. Such sulphonic acidscan be sulphurized. Whether sulphurized or non-sulphurized thesesulphonic acids are believed to have surfactant properties comparable tothose of sulphonic acids, rather than surfactant properties comparableto those of phenols.

Sulphonic acids suitable for use in accordance with the invention alsoinclude alkyl sulphonic acids. In such compounds the alkyl groupsuitably contains 9 to 100 carbon atoms, advantageously 12 to 80 carbonatoms, especially 16 to 60 carbon atoms.

In one aspect of the invention, the surfactant system is derivable fromat least one sulphurized phenol or a derivative thereof and at least onesulphonic acid or a derivative thereof. In this case, the proportions,measured as described herein, of phenol to sulphonic acid are preferablyin the range of from 15:85 to 95:5 mass %, preferably 30:70 to 70:30mass %, especially 40:60 to 60:40 mass %.

In another aspect of the invention the surfactant system is derivablefrom at least one sulphurized phenol or a derivative thereof, at leastone salicylic acid or a derivative thereof, and at least one sulphonicacid or a derivative thereof. In this case, the proportions, measured asdescribed herein, of phenol to salicylic acid to sulphonic acid in thesurfactant system are advantageously in the range of from 15 to 90 mass%: 5 to 90 mass %: 20 to 80 mass %: preferably 20 to 80 mass %: 20 to 80mass %: 10 to 50 mass %: especially 30 to 50 mass %: 25 to 45 mass %: 15to 35 mass %.

If desired, at least one of the surfactants from which the surfactantsystem in the overbased detergent is derivable may be a carboxylic acid.

Carboxylic acids which may be used in accordance with the inventioninclude mono- and dicarboxylic acids. Preferred monocarboxylic acids arethose containing 1 to 30 carbon atoms, especially 8 to 24 carbon atoms.(Where this specification indicates the number of carbon atoms in acarboxylic acid, the carbon atom(s) in the carboxylic group(s) is/areincluded in that number.) Examples of monocarboxylic acids areiso-octanoic acid, stearic acid, oleic acid, palmitic acid and behenicacid. Iso-octanoic acid may, if desired, be used in the form of themixture of C8 acid isomers sold by Exxon Chemical under the trade name“Cekanoic”. Other suitable acids are those with tertiary substitution atthe α-carbon atom and dicarboxylic acids with more than 2 carbon atomsseparating the carboxylic groups. Further, dicarboxylic acids with morethan 35 carbon atoms, for example, 36 to 100 carbon atoms, are alsosuitable. Unsaturated carboxylic acids can be sulphurized. Althoughsalicylic acids contain a carboxylic group, for the purposes of thepresent specification they are considered to be a separate group ofsurfactants, and are not considered to be carboxylic acid surfactants.(Nor, although they contain a hydroxyl group, are they considered to bephenol surfactants.)

In one aspect of the invention, where a carboxylic acid/derivative isused, this is not (a) an acid of the formula R^(a)—CH(R^(b))—COOH,wherein R^(a) represents an alkyl or alkenyl group containing 10 to 24carbon atoms and R^(b) represents hydrogen, an alkyl group with 1 to 4carbon atoms, or a CH₂COOH group, or an acid anhydride, acid chloride orester thereof, or (b) a di- or polycarboxylic acid containing from 36 to100 carbon atoms or an acid anhydride, acid chloride or ester thereof.In another aspect of the invention, the carboxylic acid/derivative, ifused, has 8 to 11 carbon atoms in the carboxylic-containing moiety.

In a further aspect of the invention, where a carboxylic acid/derivativeis used, this is not a monocarboxylic acid/derivative with more than 11carbon atoms in the carboxylic-containing moiety. In another aspect, thecarboxylic acid/derivative is not a dicarboxylic acid/derivative withmore than 11 carbon atoms in the carboxylic-containing moiety. In afurther aspect, the carboxylic acid/derivative is not a polycarboxylicacid/derivative with more than 11 carbon atoms in thecarboxylic-containing moiety. In another aspect, a carboxylic addsurfactant is not a hydrocarbyl-substituted succinic acid or aderivative thereof.

In one aspect of the invention, the surfactant system is derivable fromat least one sulphurized phenol or a derivative thereof, at least onesulphonic acid or a derivative thereof, and at least one carboxylic acidor derivative thereof. In this case, the proportions, measured asdefined herein, of phenol to sulphonic acid to carboxylic acid arepreferably in the range of from 15 to 90:5 to 90:5 to 90 mass %;preferably 20 to 80:10 to 50:10 to 50 mass %; especially 30 to 70:10 to30:10 to 30 mass %.

Examples of other surfactants which may be used in accordance with theinvention include the following compounds, and derivatives thereof:naphthenic acids, especially naphthenic acids containing one or morealkyl groups, dialkylphosphonic acids, dialkylthiophosphonic acids, anddialkyldithiophosphoric acids, high molecular weight (preferablyethoxylated) alcohols, dithiocarbamic acids, thiophosphines, anddispersants. Surfactants of these types are well known to those skilledin the art.

Where a surfactant is used in the form of a salt, any suitable cationmay be present, for example, a quatemary nitrogenous ion, or,preferably, a metal ion. Suitable metal ions include those of alkalimetals, alkaline earth metals (including magnesium) and transitionmetals. Examples of suitable metals are lithium, potassium, sodium,magnesium, calcium, barium, copper, zinc, and molybdenum. Preferredmetals are lithium, potassium, sodium, magnesium and calcium, morepreferably lithium, sodium, magnesium and calcium, especially calcium.Neutralization of surfactants may be effected before addition of thebasic calcium compound(s) (b) used in the overbasing step or by means ofthe said basic calcium compound.

If desired, a mixture of two or more members of any one group ofsurfactants may be used in preparing overbased detergents in accordancewith the invention, provided that at least one surfactant from adifferent group is also present. Thus, for example, many processes forintroducing substituents into aromatic rings will result in a mixture ofcompounds, and it is normally convenient to use such a mixture withoutseparating its components from one another.

Where in this specification an overbased detergent is said to beprepared from certain specified surfactants, for example, a phenolsurfactant and a sulphonic acid surfactant, or a phenol surfactant, asulphonic acid surfactant and a carboxylic acid surfactant, or phenolsurfactant, a salicylic acid surfactant and a sulphonic acid surfactant,the total proportion of those surfactants (in free form) in thesurfactant system of the overbased detergent is advantageously at least75 mass %, preferably at least 85 mass %, especially at least 95 mass %.

The invention makes it possible, if desired, to obtain high TBNoverbased phenate detergents while minimizing the amount of the(relatively expensive) surfactant component of the overbased detergent:thus, the invention makes it possible to obtain phenate overbaseddetergents with a relatively high TBN: % surfactant ratio. This is ofparticular advantage in the case of lubricants for marine use, as marineengines require relatively large amounts of lubricants containing highTBN overbased detergents (for example, Marine Diesel Cylinder Lubricants(MDCL) are “once through” lubricants), but is also of advantage in thecase of other lubricants, for example, crankcase lubricants. Further,the invention makes it possible to provide highly effective overbaseddetergents having a relatively low viscosity, even when the surfactantsystem contains a relatively high proportion of phenate/salicylate.

High TBN calcium overbased sulphonates and carboxylates with lowviscosities were previously known. The provision of calcium overbaseddetergents comprising a surfactant system which can, if desired, containa relatively high proportion of phenate, thus giving good performancelevels in a number of applications, for example, in marine lubricants,while minimising the amount of relatively expensive surfactant required,and which may also have a high TBN and low viscosity, represents asignificant technical advance.

Further, previously proposed processes for preparing overbased phenatedetergents typically employed relatively high carbonation temperatures,for example, temperatures of more than 100° C. and, in many priorproposals, the use of a surfactant such as certain carboxylic acidshaving at least 12 carbon atoms was taught as being essential forobtaining a satisfactory product. In accordance with the presentinvention, carbonation is carried out at lower temperatures, and can becarried out without reagents such as glycols necessary when operating athigher temperatures. Furthermore, satisfactory products can be obtainedwithout the use of certain carboxylic acids having at least 12 carbonatoms previously taught to be essential.

As indicated above, the overbased detergents according to the inventionare preferably hybrid overbased detergents, that is, overbaseddetergents obtained by overbasing a mixture containing two or moresurfactants. Such hybrid detergents have the advantage of making itpossible to provide an overbased detergent system having propertiescontributed by two or more surfactants without the need to manufactureand blend two or more separate overbased detergents. Further,elimination of the need to blend separate overbased detergents givesmore flexibility as to the final TBN, surfactant proportions, and theTBN: % surfactant ratios, and may also overcome problems ofincompatibility or stability that may be experienced when preparingblends containing separate overbased detergents.

More particularly, the hybrid overbased detergents of the presentinvention have been found to give rise to improved stability when usedin formulating lubricating oils, for example, for trunk piston marinediesel engines, i.e. medium-speed marine diesel engines. In particular,when formulating such oils to contain phenate, sulfonate and salicylatesurfactant anions, greater stability, as measured by the percent volumesediment reduction in stored oil, is achieved when two or more of thoseanions are provided in the oil in the form of a complex detergent of thepresent invention. This is in comparison with such oils where the threeanions are provided separately in the oil.

For example, an oil formulated with a phenate:sulfonate hybrid overbaseddetergent of the invention and a salicylate provided separately, and anoil formulated with a phenate:sulfonate:salicylate hybrid overbaseddetergent of the invention each has greater stability than a comparableoil formulated with a phenate, a sulfonate and a salicylate eachprovided separately.

Overbased detergents in accordance with, or prepared in accordance with,the invention, which are normally prepared as concentrates in oilcontaining, for example, 50 to 70 mass % overbased detergent based onthe mass of the concentrate, are useful as additives for oil-basedcompositions, for example, lubricants or greases, and the invention thusalso provides such compositions containing the overbased detergents, andconcentrates for use in preparing such compositions. The amount ofoverbased detergent to be included in the oil-based composition dependson the type of composition and its proposed application: lubricants formarine applications typically contain 0.5 to 18 mass % of overbaseddetergent, on an active ingredient basis based on the final lubricant,while automotive crankcase lubricating oils typically contain 0.01 to 6mass % of overbased detergent, on an active ingredient basis based onthe final lubricant

Overbased detergents in accordance with, or prepared in accordance with,the invention, are oil-soluble or (in common with certain of the otheradditives referred to below) are dissolvable in oil with the aid of asuitable solvent, or are stably dispersible materials. Oil-soluble,dissolvable, or stably dispersible as that terminology is used hereindoes not necessarily indicate that the additives are soluble,dissolvable, miscible, or capable of being suspended in oil in allproportions. It does mean, however, that the additives are, forinstance, soluble or stably dispersible in oil to an extent sufficientto exert their intended effect in the environment in which the oil isemployed. Moreover, the incorporation in an oil-based composition ofother additives may permit incorporation of higher levels of aparticular additive, if desired.

The overbased detergents may be incorporated into a base oil in anyconvenient way. Thus, they may be added directly to the oil bydispersing or by dissolving them in the oil at the desired level ofconcentration, optionally with the aid of a suitable solvent such, forexample, as toluene or cyclohexane. Such blending can occur at roomtemperature or at elevated temperature.

Overbased detergents according to, or prepared in accordance with, theinvention are particularly useful in lubricating oil compositions whichemploy a base oil in which the mixtures are dissolved or dispersed. Baseoils with which the overbased detergents may be used include thosesuitable for use as crankcase lubricating oils for spark-ignited andcompression-ignited internal combustion engines, for example, automobileand truck engines, and marine diesel engines. As indicated above, theoverbased detergents are of particular utility in lubricants for use inmarine engines.

Synthetic base oils include alkyl esters of dicarboxylic acids,polyglycols and alcohols; poly-α-olefins, including polybutenes; alkylbenzenes; organic esters of phosphoric acids; and polysilicone oils.

Natural base oils include mineral lubricating oils which may vary widelyas to their crude source, for example, as to whether they areparaffinic, naphthenic, mixed, or paraffinic-naphthenic, as well as tothe method used in their production, for example, their distillationrange and whether they are straight run or cracked, hydrofined, orsolvent extracted.

Lubricating oil base stocks suitable for use in crankcase lubricantsconveniently have a viscosity of about 2.5 to about 12 cSt, or mm²/s, at100° C., although base stocks with other viscosities may be used, forexample, bright stock.

Lubricating oil base stocks suitable for use in marine lubricantsconveniently have a viscosity of typically about 3 to about 15 cSt, ormm²/s, at 100° C., although base stocks with other viscosities may alsobe used. Thus, for example, bright stocks, which typically have aviscosity of about 30 to 35 cSt, or mm²/s, at 100° C. may be used.

An overbased detergent in accordance with, or prepared in accordancewith, the present invention may be employed in a lubricating oilcomposition which comprises lubricating oil, typically in a majorproportion, and the overbased detergent, typically in a minorproportion. Additional additives may be incorporated in the compositionto enable It to meet particular requirements. Examples of additionaladditives which may be included in lubricating oil compositionscontaining an overbased detergent in accordance with the invention areviscosity index improvers, corrosion inhibitors, other oxidationinhibitors or antioxidants, friction modifiers, dispersants, otherdetergents, metal rust inhibitors, anti-wear agents, pour pointdepressants, and anti-foaming agents. Lubricating oils suitable for usein marine engines advantageously include a dispersant and an antiwearagent as additional additives and may also contain other additives, forexample, additional antioxidants, antifoaming agents and/or rustinhibitors. Certain of the additional additives specified below are moreappropriate for use in lubricants for automobile engines than for use inlubricants for marine engines.

Viscosity index improvers (or viscosity modifiers) impart high and lowtemperature operability to a lubricating oil and permit it to remainshear stable at elevated temperatures and also exhibit acceptableviscosity or fluidity at low temperatures. Suitable compounds for use asviscosity modifiers are generally high molecular weight hydrocarbonpolymers, including polyesters, and viscosity index improverdispersants, which function as dispersants as well as viscosity indeximprovers. Oil-soluble viscosity modifying polymers generally haveweight average molecular weights of from about 10,000 to 1,000,000,preferably 20,000 to 500,000, as determined by gel permeationchromatography or light scattering methods.

Corrosion inhibitors reduce the degradation of metallic parts contactedby the lubricating oil composition. Thiadiazoles, for example thosedisclosed in U.S. Pat. Nos. 2,719,125, 2,719,126 and 3,087,932, areexamples of corrosion inhibitors for lubricating oils.

Oxidation inhibitors, or antioxidants, reduce the tendency of mineraloils to deteriorate in service, evidence of such deterioration being,for example, the production of varnish-like deposits on metal surfacesand of sludge, and viscosity increase. Suitable oxidation inhibitorsinclude sulphurized alkyl phenols and alkali or alkaline earth metalsalts thereof; diphenylamines; phenyl-naphthylamines; andphosphosulphurized or sulphurized hydrocarbons.

Other oxidation inhibitors or antioxidants which may be used inlubricating oil compositions comprise oil-soluble copper compounds. Thecopper may be blended into the oil as any suitable oil-soluble coppercompound. By oil-soluble it is meant that the compound is oil-solubleunder normal blending conditions in the oil or additive package. Thecopper may, for example, be in the form of a copper dihydrocarbyl thio-or dithio-phosphate. Alternatively, the copper may be added as thecopper salt of a synthetic or natural carboxylic acid, for example, a C₈to C₁₈ fatty acid, an unsaturated acid, or a branched carboxylic acid.Also useful are oil-soluble copper dithiocarbamates, sulphonates,phenates, and acetylacetonates. Examples of particularly useful coppercompounds are basic, neutral or acidic copper Cu^(I) and/or Cu^(II)salts derived from alkenyl succinic acids or anhydrides.

Copper antioxidants will generally be employed in an amount of fromabout 5 to 500 ppm by weight of the copper, in the final lubricatingcomposition.

Friction modifiers and fuel economy agents which are compatible with theother ingredients of the final oil may also be included. Examples ofsuch materials are glyceryl monoesters of higher fatty acids, esters oflong chain polycarboxylic acids with diols, oxazoline compounds, andoil-soluble molybdenum compounds.

Dispersants maintain oil-insoluble substances, resulting from oxidationduring use, in suspension in the fluid, thus preventing sludgeflocculation and precipitation or deposition on metal parts. So-calledashless dispersants are organic materials which form substantially noash on combustion, in contrast to metal-containing (and thusash-forming) detergents. Borated metal-free dispersants are alsoregarded herein as ashless dispersants. Suitable dispersants include,for example, derivatives of long chain hydrocarbon-substitutedcarboxylic acids in which the hydrocarbon groups contain 50 to 400carbon atoms, examples of such derivatives being derivatives of highmolecular weight hydrocarbyl-substituted succinic acid. Suchhydrocarbyl-substituted carboxylic acids may be reacted with, forexample, a nitrogen-containing compound, advantageously a polyalkylenepolyamine, or with an ester. Particularly preferred dispersants are thereaction products of polyalkylene amines with alkenyl succinicanhydrides.

A viscosity index improver dispersant functions both as a viscosityindex improver and as a dispersant. Examples of viscosity index improverdispersants suitable for use in lubricating compositions includereaction products of amines, for example polyamines, with ahydrocarbyl-substituted mono- or dicarboxylic acid in which thehydrocarbyl substituent comprises a chain of sufficient length to impartviscosity index improving properties to the compounds.

Examples of dispersants and viscosity index improver dispersants may befound in EP-A-24146.

Additional detergents and metal rust inhibitors include the metal salts,which may be overbased, of sulphonic acids, alkyl phenols, sulphurizedalkyl phenols, alkyl salicylic acids, thiophosphonic acids, naphthenicacids, and other oil-soluble mono- and dicarboxylic acids.Representative examples of detergents/rust inhibitors, and their methodsof preparation, are given in EP-A-208 560.

Antiwear agents, as their name implies, reduce wear of metal parts. Zincdihydrocarbyl dithiophosphates (ZDDPs) are very widely used as antiwearagents. Especially preferred ZDDPs for use in oil-based compositions arethose of the formula Zn[SP(S)(OR¹)(OR²)]₂ wherein R¹ and R² contain from1 to 18, and preferably 2 to 12, carbon atoms.

Pour point depressants, otherwise known as lube oil flow improvers,lower the minimum temperature at which the fluid will flow or can bepoured. Such additives are well known. Foam control may be provided byan antifoamant of the polysiloxane type, for example, silicone oil orpolydimethyl siloxane.

Some of the above-mentioned additives may provide a multiplicity ofeffects; thus for example, a single additive may act as adispersant-oxidation inhibitor. This approach is well known and need notbe further elaborated herein.

When lubricating compositions contain one or more of the above-mentionedadditives, each additive is typically blended into the base oil in anamount which enables the additive to provide its desired function.Representative effective amounts of such additives, when used incrankcase lubricants, are as follows:

Mass % a.i.* Mass % a.i.* Additive (Broad) (Preferred) ViscosityModifier 0.01-6 0.01-4 Corrosion Inhibitor 0.01-5 0.01-1.5 OxidationInhibitor 0.01-5 0.01-1.5 Friction Modifier 0.01-5 0.01-1.5 Dispersant0.1-20 0.1-8 Detergents/rust inhibitors 0.01-6 0.01-3 Anti-wear Agent0.01-6 0.01-4 Pour Point Depressant 0.01-5 0.01-1.5 Anti-Foaming Agent0.001-3 0.001-0.15 Mineral or Synthetic Base Oil Balance Balance *Mass %active ingredient based on the final oil.

Typical proportions for additives for a TPEO (a trunk piston engine oil)are as follows:

Mass % a.i.* Mass % a.i.* Additive (Broad) (Preferred) Detergent 0.5 -102-7 Dispersant(s) 0.5-5 1-3 Anti-wear agent(s) 0.1-1.5 0.5-1.3 Oxidationinhibitor 0.2-2 0.5-1.5 Rust inhibitor 0.03-0.15 0.05-0.1 Pour pointdepressant 0.03-0.15 0.05-0.1 Mineral or synthetic base oil BalanceBalance *Mass % active ingredient based on the final oil.

Typical proportions for additives for a MDCL (a marine diesel cylinderlubricant) are as follows:

Mass % a.i.* Mass % a.i.* Additive (Broad) (Preferred) Detergent(s) 1-183-12 Dispersant(s) 0.5-5 1-3 Anti-wear agent(s) 0.1-1.5 0.5-1.3 Pourpoint depressant 0.03-0.15 0.05-0.1 Mineral or synthetic base oilBalance Balance *Mass % active ingredient based on the final oil.

When a plurality of additives are employed it may be desirable, althoughnot essential, to prepare one or more additive packages comprising theadditives, whereby several additives can be added simultaneously to thebase oil to form the lubricating oil composition. Dissolution of theadditive package(s) into the lubricating oil may be facilitated bysolvents and by mixing accompanied with mild heating, but this is notessential. The additive package(s) will typically be formulated tocontain the additive(s) in proper amounts to provide the desiredconcentration in the final formulation when the additive package(s)is/are combined with a predetermined amount of base lubricant. Thus, oneor more overbased detergents in accordance with the present inventionmay be added to small amounts of base oil or other compatible solventstogether with other desirable additives to form additive packagescontaining active ingredients in an amount, based on the additivepackage, of, for example, from about 2.5 to about 90 mass %, andpreferably from about 5 to about 75 mass %, and most preferably fromabout 8 to about 60 mass % by weight, additives in the appropriateproportions with the remainder being base oil.

The final formulations may typically contain about 5 to 40 mass % of theadditive package(s) with the remainder being base oil.

The following Examples illustrate the invention.

EXAMPLE 1

540 g toluene, 276 g methanol, 22 g water, and 22 g of diluent oil (150N) were introduced into a reactor and mixed while maintaining thetemperature at approximately 20° C. Calcium hydroxide (Ca(OH)₂) (145 g)was added, and the mixture was heated to 40° C., with stirring. To theslurry obtained in this way was added a mixture, maintained at 40° C.,of the phenol and sulphonic acid surfactants specified in Table 1 and100 g toluene, followed by a further quantity (50 g) of toluene.

After neutralization of the surfactants by the calcium hydroxide, thetemperature of the mixture was reduced to approximately 28° C., and wasmaintained at approximately 28° C. while carbon dioxide was injectedinto the mixture at a rate such that substantially all the carbondioxide was absorbed in the reaction mixture to form the basic material.The temperature was then raised to 60° C. over 60 minutes, followingwhich the mixture was cooled to a temperature of approximately 28° C.over 30 minutes. At 28° C., a further quantity of calcium hydroxide (127g) was added and carbon dioxide (62 g) was charged. After this secondcarbonation step, the temperature was raised to 60° C. over 90 minutes.

Subsequently, the volatile materials were distilled off, a second chargeof diluent oil (267 g) was introduced, and the product was filtered toremove sediment.

Details of the starting materials used in all the Examples are given inTable 1 and the notes thereon. The quantity of diluent oil (SN150) inTable 1 is the total amount charged. Table 2 gives the TBN, the % totalsurfactant (Y, determined as described herein) and the TBN: % totalsurfactant ratio (X, determined as described herein), the standardizedTBN, and the proportions of individual surfactants in the surfactantsystem of the overbased detergent (see Note 2 to Tables 1 and 2) of theoverbased detergent, together with viscosity data and the filtrationrate (in kg/m²/h) and filtration gradient.

EXAMPLES 2 to 23

The method indicated in Example 1 was repeated, using the startingmaterials, and proportions of starting materials, indicated in Table 1and the notes thereon, and using amounts of toluene, methanol and waterwithin the following ranges: toluene—500 to 690 g; methanol—270 to 330g; water—15 to 25 g. Characteristics of the overbased detergentsobtained are specified in Table 2.

In Examples 5 to 8, 15 g of formic acid was also introduced into thereactor.

In Example 12, SN600 oil was used instead of SN150 oil.

In Examples 2, 4, 9, 10, and 18 to 22, the product was filtered insolvents, after removal of polar solvents.

In Example 17, carbonation was carried out at 30° C.

In Example 23 there was an additional (third) calcium hydroxideaddition, carbon dioxide addition, and heat-soaking sequence, carriedout under the conditions indicated in Example 1 for the second suchsequence, except that each heat-soaking step was carried out as in thefirst sequence.

The production of the overbased detergents according to the presentinvention may be associated with evolution of sulphur compounds such ashydrogen sulphide and mercaptans, particularly when the detergent isrequired, for operational reasons, to be maintained at elevatedtemperature, such as above 130° C., for extended periods, followingdistilling off the volatile materials and prior to filtration to removesediment.

Such evolution is undesirable because it interferes with safe andhygienic plant operation. One way of preventing or ameliorating suchevolution is by olefin treatment at any stage in the production of thedetergent. For example, the olefin can be incorporated at any stage ofraw material preparation, neutralisation, overbasing, volatile materialdistillation, or period spent at elevated temperature, i.e. at any stagein the preparation of the detergent. Incorporation during solventdistillation is preferred, e.g. at about 130° C.

Any olefin that can remain in solution or in dispersion in the detergentat elevated temperature can be used. Examples of such olefins are thosewith high or low substitution having from 18 to 60 carbon atoms or more.Specific examples of such olefins are n-octadecene; an olefin mixturehaving, on average, 24 carbon atoms; and oligomers of butene. A suitabletreat rate of the olefin is from 0.1 to 5 or more mass/% based in thefinished detergent, preferably 0.1 to 2 mass/%.

TABLE 1 Charges for Examples 1 to 23 Phenol Sulphonic Salicylic (g)+acid (g) + acid (g) + Carboxylic Ca(OH)₂ SN150 Ex. No. source sourcesource Acid (g) CO₂ (g) (g) (g) 1 239 (2)  88 (3) 0 0 124 272 289 2 96(1) 52 (1) 0 17   64 156 163 3 229 (3)  109 (3)  0 0 124 268 254 4 88(1) 58 (1) 0 17   64 155 152 5 88 (1) 75 (2) 0 17   54 155 112 6 88 (1)58 (4) 0 17   54 156 135 7 88 (1) 58 (5) 0 17   54 155 135 8 88 (1) 58(1) 0 15   62 150 135 9 84 (1) 145 (2)  0 0  90 210 191 10 85 (1) 34 (1)0 0  64 154 144 +44 (2)  11 223 (2)  83 (3) 0 0 127 275 282 12 238 (3) 110 (3)  0 0 124 272 267 13 229 (3)  109 (3)  0 0 124 268 245 14 183(5)  88 (3) 0 0 124 265 150 15 Product of Example 14 diluted with SN 15016 180 (5)  86 (3) 0 0 162 340 181 17 231 (5)  111 (3)  0 0 124 271 26718 60 (1) 53 (1) 79  0  64 150 119 19 48 (1) 61 (1) 78  0  64 149 125 2048 (1) 30 (1) 78  0  64 149 108 +39 (2)  21 123 (1)  43 (2) 71  0  64151 176 22 48 (1) 79 (2) 78  0  64 143  93 23 182 (3)  55 (3) 212  0 124266  22

TABLE 2 Properties for Examples 1 to 23 % Total TBN:% Ex. Surf. TotalSurf. Stand. Sulph Sal Carbox Kv₄₀ Kv₁₀₀ Filt. Filt. No. TBN (mass)Ratio TBN Ph % % % % mm²/s mm²/s Rate Grad. 1 407 17 24 724 59 41 0 0 6001  205  301 0.47 2 424 20 21 695 40 44 0 16  —  751 3142 — 3 411 2021 674 50 50 0 0  3685  150  649 0.56 4 424 20 21 690 36 48 0 16  —  2471696 — 5 447 21 21 731 36 48 0 16  — 9155 — — 6 417 20 21 691 36 48 016  — — — — 7 423 20 21 701 36 48 0 16  — 1044 — — 8 442 18 25 748 43 570 0 — — — — 9 420 19 22 669 27 73 0 0  2555  150 1357 — 10 423 18 24 68138 62 0 0  8670  271  479 — 11 420 17 25 776 59 41 0 0 55200 1120  2620.57 12 409 19 22 703 54 46 0 0 26060  441  304 0.53 13 416 20 21 750 5050 0 0 —  154  297 0.52 14 520 20 26 818 50 50 0 0 — 1087 — — 15 500 1926 787 50 50 0 0 —  808 — — 16 557 17 33 853 50 50 0 0 — 2049 — — 17 41220 21 744 50 50 0 0 —  148  353 0.48 18 430 18 24 699 27 47 26  0 19988 608 1242 — 19 432 19 23 688 21 54 25  0  3533  173 4525 — 20 428 19 23687 21 54 25  0 12162  502 2410 — 21 357 17 21 555 50 28 22  0  6416 206 4427 — 22 424 20 21 691 21 54 25  0 30832 1187 2410 — 23 498 24 21768 39 24 37  0 — 4289 — —

Notes on Tables 1 and 2

1. The sources of the phenol, sulphonic acid, salicylic acid andcarboxylic acid surfactants (see Table 1) are given in Table 3 below. Inthat table:

a.i.=the percentage by mass of the surfactant-containing material ascharged to the reaction vessel that is not diluent oil.

r.i.=percentage by mass of “reactive ingredient”, that is, percentage ofthe surfactant as charged to the reaction vessel that, in the liquidoverbased detergent, is associated with calcium.

(It will be appreciated that the term “active ingredient” has its normalmeaning, and refers to that portion of the surfactant-containingmaterial which comprises molecules other than diluent oil molecules. Wehave found that, when using surfactants to prepare overbased detergentsin accordance with the invention, in some cases a proportion of thesurfactant molecules do not react with the basic calcium compound(s),and remain in unreacted, non-salt, form in the liquid overbaseddetergent. In such cases, the percentage of “reactive ingredient” willbe lower than the percentage of “active ingredient”.)

2. In Table 2, Ph %, Sulph %, Sal % and Carbox % are the percentages bymass of the phenol surfactant, sulphonic acid surfactant, salicylic acidsurfactant and carboxylic acid surfactant respectively (in hydrolyzedform), based on the mass of the total surfactant (in hydrolyzed form)associated with the basic calcium compound in the overbased detergent.

TABLE 3 Surfactant sources in Tables 1 and 2 Surfactant DescriptionPhenol source 1 A sulphurized alkyl phenol, synthesized from sulphurdichloride and a 65/35 (by mass) blend of tertiary nonyl (tripropylene)phenols (predominantly para- substituted) and tertiary dinonyl phenols(predominantly 2,4-substituted). (a.i. = 70; r.i. = 40) Phenol source 2A sulphurized alkyl phenol, synthesized from sulphur monochloride and a65/35 (by mass) blend of tertiary nonyl (tripropylene) phenols(predominantly para-substituted) and tertiary dinonyl phenols(predominantly 2,4- substituted). (a.i. = 72; r.i. = 40) Phenol source 3A sulphurized alkyl phenol, synthesized from sulphur monochloride and a65/35 (by mass) blend of tertiary nonyl (tripropylene) phenols(predominantly para-substituted) and tertiary dinonyl phenolspredominantly 2,4- substituted). (a.i. = 84; r.i. = 40) Sulphonic acidAn alkyl benzene sulphonic acid, derived from SO₃ (in liquid SO₂) with asource 1 molecular weight of 495 (a.i. = 100; r.i. = 90) Sulphonic acidAn alkyl benzene sulphonic acid, derived from SO₃ (in liquid SO₂) with asource 2 molecular weight of 683 (a.i. = 76; r.i. = 70) Sulphonic acidAn alkyl benzene sulphonic acid, derived from SO₃ (in Liquid 502) with asource 3 molecular weight of 683 (a.i. = 96; r.i. = 84) Sulphonic acidAn alkyl benzene sulphonic acid, derived from SO₃ (in Liquid SO₂) with asource 4 molecular weight of 365 (a.i. = 97; r.i. = 90) Sulphonic acidAn alkyl benzene sulphonic acid, derived from 503 (in Liquid 502) with asource 5 molecular weight of 440 (a.i. = 100; r.i. = 90) Salicylic acidA low base number calcium alkyl salicylate (TBN = 64) from ShellChemicals Ltd. (a.i. = 50; r.i. = 35) Carboxylic acid Cekanoic acid,substantially C8 (a.i. = 100; r.i. = 100)

What is claimed is:
 1. A calcium overbased detergent formed by treatingwith an overbasing agent, a mixture containing at least one basiccalcium compound and a surfactant system comprising at least twosurfactants, at least one of which is a sulphurized or non-sulphurizedphenol or a derivative thereof and at least one other surfactant isother than a phenol surfactant, the proportion of the said phenol in thesurfactant system being at least 15 mass %, and the overbased detergenthaving a TBN: % surfactant ration of at least
 21. 2. An overbaseddetergent as claimed in claim 1, wherein the proportion of the phenol inthe surfactant system is at least 25 mass %.
 3. An overbased detergentas claimed in claim 1, wherein the phenol is an alkyl-substitutedphenol.
 4. An overbased detergent as claimed in claim 1, wherein atleast one of the surfactants from which the surfactant system is derivedis a sulphonic acid or a derivative thereof.
 5. An overbased detergentas claimed in claim 4, wherein the sulphonic acid is analkyl-substituted aryl sulphonic acid.
 6. An overbased detergent asclaimed in claim 4, wherein the total proportion of the said phenol andthe said sulphonic acid in the surfactant system is at least 75 mass %.7. An overbased detergent as claimed in claim 4, wherein the surfactantsystem is derived from at least one sulphurized phenol and at least onesulphonic acid, the proportions of phenol to sulphonic acid in thesurfactant system being in the range of from 15:85 to 95:5 mass %.
 8. Anoverbased detergent as claimed in claim 4, wherein at least one of thesurfactants from which the surfactant system is derived is a carboxylicacid.
 9. An overbased detergent as claimed in claim 8, wherein thecarboxylic acid/derivative is other than (a) an acid of the formulaR^(a)—CH(R^(b))—COOH, wherein R^(a) represents an alkyl or alkenyl groupcontaining 10 to 24 carbon atoms and R^(b) represents hydrogen, an alkylgroup with 1 to 4 carbon atoms, or a CH₂COOH group, or an acidanhydride, acid chloride or ester thereof, and (b) a di- orpolycarboxylic acid containing from 36 to 100 carbon atoms or an acidanhydride, acid chloride or ester thereof.
 10. An overbased detergent asclaimed in claim 8, wherein the carboxylic acid/derivative has 8 to 11carbon atoms in the carboxylic-containing moiety.
 11. An overbaseddetergent as claimed in claim 8, wherein the total proportion of thesaid phenol, the said sulphonic acid and the said carboxylic acid in thesurfactant system is at least 75 mass %.
 12. An overbased detergent asclaimed in claim 8, wherein the surfactant system is derived from atleast one sulphurized phenol, at least one sulphonic acid and at leastone carboxylic acid, the proportions of phenol to sulphonic acid tocarboxylic acid being in the range of from 15 to 90:5 to 90:5 to 90mass%.
 13. An overbased detergent as claimed in claim 4, wherein atleast one of the surfactants from which the surfactant system is derivedis a sulphurized or non-sulphurized salicylic acid.
 14. An overbaseddetergent as claimed in claim 13, wherein the salicylic acid is analkyl-substituted salicylic acid.
 15. An overbased detergent as claimedin claim 13, wherein the total proportion of the said phenol, the saidsalicylic acid and the said sulphonic acid in the surfactant system isat least 75 mass %.
 16. An overbased detergent as claimed in claim 15,wherein the surfactant system is derived from at least one sulphurizedphenol, at least one salicylic acid, and at least one sulphonic acid,the proportions of phenol to salicylic acid to sulphonic acid in thesurfactant system being in the range of from 15 to 90 mass %: 5 to 90mass %: 20 to 80 mass %.
 17. An overbased detergent as claimed in claim1, which is substantially free from inorganic halides or ammonium salts,and groups or compounds derived from such compounds.
 18. An overbaseddetergent as claimed in claim 1, which is substantially free fromdihydric alcohols and groups or compounds derived from dihydricalcohols.
 19. An overbased detergent as claimed in claim 1, having a TBNof at least
 300. 20. An overbased detergent as claimed in claim 1,having a standardized TBN of at least
 450. 21. An overbased detergent asclaimed in claim 1, having a viscosity at 40° C. of at most 20,000mm²/s.
 22. An overbased detergent as claimed in claim 1, having aviscosity at 100° C. of at most 2000 mm²/s.
 23. A method ofmanufacturing a calcium overbased detergent having a surfactant systemderived from at least two surfactants, which method comprises treatingwith an overbasing agent a mixture comprising: (a) at least twosurfactants, at least one of which is a sulphurized or non-sulphurizedphenol, and another of which is a surfactant other than a phenolsurfactant; (b) at least one basic calcium compound; and (c) oil,treatment with the overbasing agent being carried out in at least onestep at less than 100° C., the total proportion of the said phenol inthe surfactant system of the overbased detergent being at least 15 mass%, and the overbased detergent having a TBN: % surfactant ratio of atleast
 21. 24. A method as claimed in claim 23, wherein treatment withthe overbasing agent is effected at a temperature of at least 15° C. 25.A method as claimed in claim 24, wherein treatment with the overbasingagent is effected at a temperature of less than 80° C.
 26. A method asclaimed in claim 23, wherein the first treatment step is followed by aheat-soaking step.
 27. A method as claimed in claim 26, whereinheat-soaking is carried out at a temperature in the range of from 15 tojust below the reflux temperature of the reaction mixture.
 28. A methodas claimed in claim 23, wherein there are two treatment steps and afurther quantity of basic calcium compound is introduced into themixture between the said two treatment steps.
 29. A method as claimed inclaim 23, wherein treatment with the overbasing agent is carried out inthree or more steps, a further quantity of basic calcium compound beingintroduced into the reaction mixture before each treatment step afterthe first.
 30. A method as claimed in claim 23, wherein the overbasingagent comprises at least one of carbon dioxide and boric acid.
 31. Amethod as claimed in claim 23, wherein the starting materials andreaction conditions are such that the overbased detergent has one ormore of the following characteristics (1) the proportion of phenol inthe surfacant system is at least 25 mass %; (2) the total proportion ofphenol and sulphonic acid in the surfacant system is at least 75 mass %;(3) the proportion of phenol to sulphonic acid in the surfacant systemis in the range of from 15:85 to 95:5 mass %; (4) the total proportionof phenol, sulphonic acid and carboxylic acid in the surfactant systemis at least 75 mass %: (5) the proportions of phenol to sulphonic acidto carboxylic acid is in the range of from 15 to 90:5 to 90:5 to 90 mass%; (6) the total proportion of phenol, salicylic acid and sulphonic acidin the surfactant system is at least 75 mass %; (7) the proportions ofphenol to salicylic acid to sulphonic acid is in the range of from 15 to90:5 to 90:20 to 80 mass %; (8) a TBN of the overbased detergent of atleast 300; (9) a standardized TBN of the overbased detergent of at least450; (10) a viscosity at 40° C. of the overbased detergent of at most20,000 mm²/s and a viscosity at 100° C. of at most 2000 mm²/s.
 32. Anoverbased detergent prepared by a method as claimed in claim
 23. 33. Anoil-based composition comprising an oil and an overbased detergent asclaimed in claim
 1. 34. A lubricating oil comprising an oil and anoverbased detergent as claimed in claim
 1. 35. A composition as claimedin claim 34, which is in the form of a concentrate.
 36. A lubricatingoil as claimed in claim 35, which is a marine engine lubricating oil.37. A method of lubricating a marine engine which comprises supplying tothe marine engine a lubricant oil as defined in claim
 35. 38. Anoverbased detergent as claimed in claim 1, wherein the overbaseddetergent has one or more of the following characteristics: (1) theproportion of phenol in the surfactant system is at least 70 mass %; (2)the total proportion of phenol and sulphonic acid in the surfactantsystem is at least 95 mass %; (3) the proportion of phenol to sulphonicacid in the surfactant system is in the range of from 40:60 to 60:40mass %; (4) the total proportion of phenol, sulphonic acid andcarboxylic acid in the surfactant system is at least 95 mass %; (5) theproportions of phenol to sulphonic acid to carboxylic acid is in therange of from 30 to 70:10 to 30:10 to 30 mass %; (6) the totalproportion of phenol, salicylic acid and sulphonic acid in thesurfactant system is at least 95 mass %; (7) the proportions of phenolto salicylic acid to sulphonic acid is in the range of from 30 to 50:25to 45:15 to 35 mass %. (8) a TBN of the overbased detergent of at least450; (9) a standardized TBN of the overbased detergent of at least 650;(10) a viscosity at 40° C. of the overbased detergent of at most 10,000mm²/s and a viscosity at 100° C. of at most 500 mm²/s.
 39. A method asclaimed in claim 23, wherein the starting materials and reactionconditions are such that the overbased detergent has one or more of thefollowing characteristics: (1) the proportion of phenol in thesurfactant system is at least 70 mass %; (2) the total proportion ofphenol and sulphonic acid in the surfactant system is at least 95 mass%; (3) the proportion of phenol to sulphonic acid in the surfactantsystem is in the range of from 40:60 to 60:40 mass %; (4) the totalproportion of phenol, sulphonic acid and carboxylic acid in thesurfactant system is at least 95 mass %; (5) the proportions of phenolto sulphonic acid to carboxylic acid is in the range of from 30 to 70:10to 30:10to 30 mass %; (6) the total proportion of phenol, salicylic acidand sulphonic acid in the surfactant system is at least 95 mass %; (7)the proportions of phenol to salicylic acid to sulphonic acid is in therange of from 30 to 50:25 to 45:15 to 35 mass %; (8) a TBN of theoverbased detergent of at least 450; (9) a standardized TBN of theoverbased detergent of at least 650; (10) a viscosity at 40° C. of theoverbased detergent of at most 10,000 mm²/s and a viscosity at 100° C.of at most 500 mm ²/s.